Methods using particulates coated with treatment chemical partitioning agents

ABSTRACT

Methods of treating a portion of a subterranean formation comprising: providing partitioned, coated particulates that comprise particulates, an adhesive substance, and a partitioning agent, and wherein the partitioning agent comprises a subterranean treatment chemical; substantially slurrying the partitioned, coated particulates in a treatment fluid to create a particulate slurry; and, placing the particulate slurry into the portion of the subterranean formation.

RELATED APPLICATIONS

The present invention is a continuation in part of U.S. patentapplication Ser. No. 10/794,076 filed on Mar. 5, 2004. Moreover, thepresent invention is related to U.S. application Ser. No. ______entitled “Methods of Using Partitioned, Coated Particulates” (HES2003-IP-011506U1P1) filed on the same date herewith, which is assignedto the assignee of the present invention, the entire disclosure of whichis incorporated herein by reference.

BACKGROUND

The present invention involves methods of preparing coated particulatesand using such coated particulates in subterranean applications such asproduction enhancement and sand control. More particularly, the presentinvention relates to methods of preparing particulates treated with anadhesive substance (such as a tackifying agent or curable resin) suchthat the particulates are able to resist sticking and clumping and neednot be immediately used once they are prepared.

Subterranean operations often use particulates coated with an adhesivesubstance such as a tackifying agent or a curable resin. One example ofa production stimulation operation using such coated particulates ishydraulic fracturing, wherein a formation is treated to increase itspermeability by hydraulically fracturing the formation to create orenhance one or more cracks or “fractures.” In most cases, a hydraulicfracturing treatment involves pumping a proppant-free, viscous fluid(known as a pad fluid) into a subterranean formation faster than thefluid can escape into the formation so that the pressure in theformation rises and the formation breaks, creating an artificialfracture or enlarging a natural fracture. Then particulates known in theart as proppant are placed into the fracture to prevent the fractureform closing when the pumping pressure is released. A portion of theproppant may be coated with an adhesive substance to control themigration of the proppant particulates and/or to control the migrationof formation sands and fines.

An example of a well completion operation using a treating fluidcontaining coated particulates is gravel packing. Gravel packingtreatments are used, inter alia, to reduce the migration ofunconsolidated formation particulates into the well bore. In gravelpacking operations, particulates known in the art as gravel are carriedto a well bore by a hydrocarbon or water treatment fluid. That is, theparticulates are suspended in a treatment fluid, which may beviscosified, and the treatment fluid is pumped into a well bore in Whichthe gravel pack is to be placed. The treatment fluid leaks off into thesubterranean zone and/or is returned to the surface while theparticulates are left in the zone. The resultant gravel pack acts as afilter to separate formation sands from produced fluids while permittingthe produced fluids to flow into the well bore. A portion of the gravelmay be coated with resin or tackifying agent, inter alia, to furtherhelp control the migration of formation fines. Typically, gravel packoperations involve placing a gravel pack screen in the well bore andpacking the surrounding annulus between the sand control screen and theformation (or casing) with gravel designed to prevent the passage offormation sands through the pack. The sand control screen is generally atype of filter assembly used to support and retain the gravel placedduring the gravel pack operation. A wide range of sizes and screenconfigurations are available to suit the characteristics of a particularwell bore, the production fluid, and the subterranean formation sands.Such gravel packs may be used to stabilize a portion of a formationwhile causing minimal impairment to well productivity. The gravel isgenerally designed to prevent formation sands from occluding the screenor migrating with the produced fluids, and the screen is generallydesigned prevent the gravel from entering the well bore.

In some situations the processes of hydraulic fracturing and gravelpacking are combined into a single treatment to provide stimulatedproduction and an annular gravel pack to reduce formation sandproduction. Such treatments are often referred to as “frac pack”operations. In some cases, the treatments are completed with a gravelpack screen assembly in place, and the hydraulic fracturing treatmentbeing pumped through the annular space between the casing and screen. Insuch a situation, the hydraulic fracturing treatment usually ends in ascreen out condition creating an annular gravel pack between the screenand casing. This allows both the hydraulic fracturing treatment andgravel pack to be placed in a single operation.

SUMMARY OF THE INVENTION

The present invention involves methods of preparing coated particulatesand using such coated particulates in subterranean applications such asproduction enhancement and sand control. More particularly, the presentinvention relates to methods of preparing particulates treated with anadhesive substance (such as a tackifying agent or curable resin) suchthat the particulates are able to resist sticking and clumping and neednot be immediately used once they are prepared.

One embodiment of the present invention provides methods of treating aportion of a subterranean formation comprising: providing partitioned,coated particulates that comprise particulates, an adhesive substance,and a partitioning agent, and wherein the partitioning agent comprises asubterranean treatment chemical; substantially slurrying thepartitioned, coated particulates in a treatment fluid to create aparticulate slurry; and, placing the particulate slurry into the portionof the subterranean formation.

Another embodiments of the present invention provides methods ofcreating a propped fracture in a portion of a subterranean formationcomprising: providing at least one fracture in the portion of thesubterranean formation; providing partitioned, coated particulates thatcomprise particulates, an adhesive substance, and a partitioning agent,and wherein the partitioning agent comprises a subterranean treatmentchemical; substantially slurrying the partitioned, coated particulatesin a treatment fluid to create a particulate slurry; and, placing theparticulate slurry into the at least one fracture in the portion of thesubterranean formation so as to deposit at least a portion of thepartitioned, coated particulates into the at least one fracture.

Another embodiments of the present invention provides methods of gravelpacking along a portion of a well bore comprising: providing a portionof a well bore; providing partitioned, coated particulates that compriseparticulates, an adhesive substance, and a partitioning agent, andwherein the partitioning agent comprises a subterranean treatmentchemical; substantially slurrying the partitioned, coated particulatesin a treatment fluid to create a particulate slurry; and, placing theparticulate slurry into the portion of the well bore so as to deposit atleast a portion of the partitioned, coated particulates into thatportion and to create a gravel pack therein.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof preferred embodiments that follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention involves methods of preparing coated particulatesand using such coated particulates in subterranean applications such asproduction enhancement and sand control. More particularly, the presentinvention relates to methods of preparing particulates treated with anadhesive substance (such as a tackifying agent or curable resin) suchthat the particulates are able to resist sticking and clumping and neednot be immediately used once they are prepared. By coating apartitioning agent onto particulates that have been treated with anadhesive substance, the methods of the present invention are capable ofat least temporarily diminishing the “tackiness” of the treatedparticulates, thus preventing or minimizing the agglomeration of theparticulates and the spreading of the adhesive substance onto equipmentsurfaces. In some embodiments of the present invention the coating usedto at least temporarily diminishing the “tackiness” of the treatedparticulates may also be a treatment chemical useful in the subterraneanenvironment. Suitable partitioning agents dissolve, degrade, orotherwise are removed from the surface of the particulate at a desiredtime such that the tackiness and/or curing performance of the adhesivesubstance is substantially restored once the partitioning agent issubstantially removed. By least temporarily diminishing the tackiness ofparticulates coated with an adhesive substance the methods of thepresent invention are able to minimize the interaction of the adhesivesubstance with a treatment fluid or an equipment surface. As usedherein, the term “tacky,” in all of its forms, generally refers to asubstance having a nature such that it is (or may be activated tobecome) somewhat sticky to the touch.

Particulates coated with adhesive substances have a tendency toagglomerate and form masses of joined particulates rather than retainingtheir individual character. In the methods of the present invention,particulates are treated with an adhesive substance such as a tackifyingagent and/or a curable resin and then the particulates are substantiallycoated with a partitioning agent to help the particulates retain theirindividual tacky or curable character. Some embodiments of the presentinvention describe methods of forming coated particulates that may becreated and then stored and or shipped before use without excessiveagglomeration even under temperature and stress loads commonlyencountered by particulates such as proppant and gravel during handlingand storage before use in a subterranean formation. In some embodimentsof the present invention, the coated particulates may be created a fewhours or several months before they are used.

Particulates suitable for use in the present invention may be comprisedof any material suitable for use in subterranean operations. Suitableparticulate materials include, but are not limited to, sand; bauxite;ceramic materials; glass materials; polymer materials; Teflon®materials; nut shell pieces; seed shell pieces; cured resinousparticulates comprising nut shell pieces; cured resinous particulatescomprising seed shell pieces; fruit pit pieces; cured resinousparticulates comprising fruit pit pieces; wood; composite particulatesand combinations thereof. Composite particulates may also be suitable,suitable composite materials may comprise a binder and a filler materialwherein suitable filler materials include silica, alumina, fumed carbon,carbon black, graphite, mica, titanium dioxide, meta-silicate, calciumsilicate, kaolin, talc, zirconia, boron, fly ash, hollow glassmicrospheres, solid glass, and combinations thereof.

In some embodiments of the present invention the particulate used may bea low quality particulate. The use of low-quality particulates may beparticularly well suited for embodiments in which the particulates areto be coated with a tackifying agent or a curable resin. This is due, atleast in part, to the fact that a coating of tackifying agent or resinmay act to improve the performance of the low quality particulates. Asused herein, the term “low-quality particulates” refers to particulatesthat do not meet at least one of the standards for sphericity,roundness, size, turbidity, acid solubility, percentage of fines, orcrush resistance as recited in American Petroleum Institute RecommendedPractices (API RP) standard numbers 56 and 58 for proppant and gravelrespectively.

The API RP's describe the minimum standard for sphericity as at least0.6 and for roundness as at least 0.6. As used herein, the terms“sphericity” and “roundness” are defined as described in the API RP'sand can be determined using the procedures set forth in the API RP's.

API RP 56 also sets forth some commonly recognized proppant sizes as6/12, 8/16, 12/20, 20/40, 30/50, 40/70, and 70/140. Similarly, API RP 58also sets forth some commonly recognized gravel sizes as 8/16, 12/20,16/30, 20/40, 30/50, and 40/60. The API RP's further note that a minimumpercentage of particulates that should fall between designated sandsizes, noting that not more than 0.1 weight % of the particulates shouldbe larger than the larger sand size and not more than a maximumpercentage (1 weight % in API RP 56 and 2 weight % in API RP 58) shouldbe smaller than the small sand size. Thus, for 20/40 proppant, no morethan 0.1 weight % should be larger than 20 U.S. Mesh and no more than 1weight % smaller than 40 U.S. Mesh.

API RP's 56 and 58 describe the minimum standard for proppant and gravelturbidity as 250 FTU or less. API RP 56 describes the minimum standardfor acid solubility of proppant as no more than 2 weight % loss whentested according to API RP 56 procedures for proppant sized between 6/12Mesh and 30/50 Mesh, U.S. Sieve Series and as no more than 3 weight %loss when tested according to API RP 56 procedures for proppant sizedbetween 40/70 Mesh and 70/140 Mesh, U.S. Sieve Series. API RP 58describes the minimum standard for acid solubility of gravel as no morethan 1 weight % loss when tested according to API RP 58 procedures. APIRP 56 describes the minimum standard for crush resistance of proppant asproducing not more than the suggested maximum fines as set forth inTable 1, below, for the size being tested: TABLE 1 Suggested MaximumFines for Proppant Subjected to Crushing Strength Mesh Size CrushingStress on Proppant Maximum Fines (U.S. Sieve Series) Force (lbs) (psi)(% by weight)  6/12 6,283 2,000 20  8/16 6,283 2,000 18 12/20 9,4253,000 16 16/30 9,425 3,000 14 20/40 12,566 4,000 14 30/50 12,566 4,00010 40/70 15,708 5,000 8  70/140 15,708 5,000 6

Similarly, API RP 58 describes the minimum standard for crush resistanceof gravel as producing not more than the suggested maximum fines as setforth in Table 1, below, for the size being tested: TABLE 2 SuggestedMaximum Fines for Gravel Subjected to Crushing Strength Mesh SizeCrushing Stress on Proppant Maximum Fines (U.S. Sieve Series) Force(lbs) (psi) (% by weight)  8/16 6,283 2,000 8 12/20 6,283 2,000 4 16/306,283 2,000 2 20/40 6,283 2,000 2 30/50 6,283 2,000 2 40/60 6,283 2,0002

Resins suitable for use as an adhesive substance of the presentinvention include all resins known in the art that are capable offorming a hardened, consolidated mass. Many such resins are commonlyused in subterranean operations, and some suitable resins include twocomponent epoxy based resins, novolak resins, polyepoxide resins,phenol-aldehyde resins, urea-aldehyde resins, urethane resins, phenolicresins, furan resins, furan/furfuryl alcohol resins, phenolic/latexresins, phenol formaldehyde resins, polyester resins and hybrids andcopolymers thereof, polyurethane resins and hybrids and copolymersthereof, acrylate resins, and mixtures thereof. Some suitable resins,such as epoxy resins, may be cured with an internal catalyst oractivator so that when pumped down hole, they may be cured using onlytime and temperature. Other suitable resins, such as furan resinsgenerally require a time-delayed catalyst or an external catalyst tohelp activate the polymerization of the resins if the cure temperatureis low (i.e., less than 250° F.), but will cure under the effect of timeand temperature if the formation temperature is above about 250° F.,preferably above about 300° F. By way of further example, selection of asuitable resin may be affected by the temperature of the subterraneanformation to which the fluid will be introduced. For subterraneanformations having a BHST ranging from about 300° F. to about 600° F., afuran-based resin may be preferred. For subterranean formations having aBHST ranging from about 200° F. to about 400° F., either aphenolic-based resin or a one-component HT epoxy-based resin may besuitable. For subterranean formations having a BHST of at least about175° F., a phenol/phenol formaldehyde/furfuryl alcohol resin may also besuitable. It is within the ability of one skilled in the art, with thebenefit of this disclosure, to select a suitable resin for use inembodiments of the present invention and to determine whether a catalystis required to trigger curing.

One resin coating material suitable for use in the proppant compositionsof the present invention is a two-component epoxy based resin comprisinga hardenable resin component and a hardening agent component. Thehardenable resin component is comprised of a hardenable resin and anoptional solvent. The second component is the liquid hardening agentcomponent, which is comprised of a hardening agent, a silane couplingagent, a surfactant, an optional hydrolyzable ester for, inter alia,breaking gelled fracturing fluid films on the proppant particles, and anoptional liquid carrier fluid for, inter alia, reducing the viscosity ofthe liquid hardening agent component. It is within the ability of oneskilled in the art with the benefit of this disclosure to determine ifand how much liquid carrier fluid is needed to achieve a viscositysuitable to the subterranean conditions.

Where the resin coating material of the present invention is afuran-based resin, suitable furan-based resins include, but are notlimited to, furfuryl alcohol, a mixture furfuryl alcohol with analdehyde, and a mixture of furan resin and phenolic resin. Where theresin coating material of the present invention is a phenolic-basedresin, suitable phenolic-based resins include, but are not limited to,terpolymers of phenol, phenolic formaldehyde resins, and a mixture ofphenolic and furan resins. Of these, a mixture of phenolic and furanresins is preferred. Where the resin coating material of the presentinvention is a HT epoxy-based resin, suitable HT epoxy-based componentsincluded, but are not limited to, bisphenol A-epichlorohydrin resin,polyepoxide resin, novolac resin, polyester resin, glycidyl ethers andmixtures thereof.

Yet another resin suitable for use in the methods of the presentinvention is a phenol/phenol formaldehyde/furfuryl alcohol resincomprising from about 5% to about 30% phenol, from about 40% to about70% phenol formaldehyde, from about 10 to about 40% furfuryl alcohol,from about 0.1% to about 3% of a silane coupling agent, and from about1% to about 15% of a surfactant. In the phenol/phenolformaldehyde/furfuryl alcohol resins suitable for use in the methods ofthe present invention, suitable silane coupling agents include, but arenot limited to, n-2-(aminoethyl)-3-aminopropyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, andn-beta-(aminoethyl)-gamma-aminopropyl trimethoxysilane. Suitablesurfactants include, but are not limited to, an ethoxylated nonyl phenolphosphate ester, mixtures of one or more cationic surfactants and one ormore non-ionic surfactants, and an alkyl phosphonate surfactant.

Tackifying agents suitable for use as an adhesive substance in thepresent invention include non-aqueous tackifying agents, aqueoustackifying agents, and silyl-modified polyamides.

One type of tackifying agent suitable for use in the present inventionis a non-aqueous tackifying agent. A particularly preferred group ofnon-aqueous tackifying agents comprise polyamides that are liquids or insolution at the temperature of the subterranean formation such that theyare, by themselves, non-hardening when introduced into the subterraneanformation. A particularly preferred product is a condensation reactionproduct comprised of a polyacid and a polyamine. Such condensationreaction products include compounds such as mixtures of C₃₆ dibasicacids containing some trimer and higher oligomers and also small amountsof monomer acids that are reacted with polyamines. Other polyacidsinclude trimer acids, synthetic acids produced from fatty acids, maleicanhydride, acrylic acid, and the like. Such acid compounds arecommercially available from companies such as Witco Corporation, UnionCamp, Chemtall, and Emery Industries. The reaction products areavailable from, for example, Champion Technologies, Inc. and WitcoCorporation. Additional compounds which may be used as non-aqueoustackifying compounds include liquids and solutions of, for example,polyesters, polycarbonates and polycarbamates, natural resins such asshellac and the like. Other suitable non-aqueous tackifying agents aredescribed in U.S. Pat. No. 5,853,048 issued to Weaver, et al. and U.S.Pat. No. 5,833,000 issued to Weaver, et al., the relevant disclosures ofwhich are herein incorporated by reference.

Non-aqueous tackifying agents suitable for use in the present inventionmay be either used such that they form non-hardening coating or they maybe combined with a multifunctional material capable of reacting with thenon-aqueous tackifying agent to form a hardened coating. A “hardenedcoating” as used herein means that the reaction of the tackifyingcompound with the multifunctional material will result in asubstantially non-flowable reaction product that exhibits a highercompressive strength in a consolidated agglomerate than the tackifyingcompound alone with the particulates. In this instance, the non-aqueoustackifying agent may function similarly to a hardenable resin.Multifunctional materials suitable for use in the present inventioninclude, but are not limited to, aldehydes such as formaldehyde,dialdehydes such as glutaraldehyde, hemiacetals or aldehyde releasingcompounds, diacid halides, dihalides such as dichlorides and dibromides,polyacid anhydrides such as citric acid, epoxides, furfuraldehyde,glutaraldehyde or aldehyde condensates and the like, and combinationsthereof. In some embodiments of the present invention, themultifunctional material may be mixed with the tackifying compound in anamount of from about 0.01 to about 50 percent by weight of thetackifying compound to effect formation of the reaction product. In somepreferable embodiments, the compound is present in an amount of fromabout 0.5 to about 1 percent by weight of the tackifying compound. Someother suitable multifunctional materials are described in U.S. Pat. No.5,839,510 issued to Weaver, et al., the relevant disclosure of which isherein incorporated by reference.

Solvents suitable for use with the non-aqueous tackifying agents of thepresent invention include any solvent that is compatible with thenon-aqueous tackifying agent and achieves the desired viscosity effect.Examples of solvents suitable for use in the present invention include,but are not limited to, butylglycidyl ether, dipropylene glycol methylether, butyl bottom alcohol, dipropylene glycol dimethyl ether,diethyleneglycol methyl ether, ethyleneglycol butyl ether, methanol,butyl alcohol, isopropyl alcohol, diethyleneglycol butyl ether,propylene carbonate, d'limonene, 2-butoxy ethanol, butyl acetate,furfuryl acetate, butyl lactate, fatty acid methyl esters, andcombinations thereof. It is within the ability of one skilled in theart, with the benefit of this disclosure, to determine whether a solventis needed to achieve a viscosity suitable to the subterranean conditionsand, if so, how much.

Aqueous tackifyier agents suitable for use in the present invention arenot significantly tacky when placed onto a particulate, but are capableof being “activated” (that is destabilized, coalesced and/or reacted) totransform the compound into a sticky, tackifying compound at a desirabletime. Such activation may occur before, during, or after the aqueoustackifyier agent is placed in the subterranean formation. In someembodiments, a pretreatment may be first contacted with the surface of aparticulate to prepare it to be coated with an aqueous tackifyier agent.Suitable aqueous tackifying agents are generally charged polymers thatcomprise compounds that, when in an aqueous solvent or solution, willform a non-hardening coating (by itself or with an activator) and, whenplaced on a particulate, will increase the continuous criticalresuspension velocity of the particulate when contacted by a stream ofwater. The aqueous tackifyier agent may enhance the grain-to-graincontact between the individual particulates within the formation (bethey proppant particulates, formation fines, or other particulates),helping bring about the consolidation of the particulates into acohesive, flexible, and permeable mass.

Examples of aqueous tackifyier agents suitable for use in the presentinvention include, but are not limited to, acrylic acid polymers,acrylic acid ester polymers, acrylic acid derivative polymers, acrylicacid homopolymers, acrylic acid ester homopolymers (such as poly(methylacrylate), poly (butyl acrylate), and poly(2-ethylhexyl acrylate)),acrylic acid ester co-polymers, methacrylic acid derivative polymers,methacrylic acid homopolymers, methacrylic acid ester homopolymers (suchas poly(methyl methacrylate), poly(butyl methacrylate), andpoly(2-ethylhexyl methacryate)), acrylamido-methyl-propane sulfonatepolymers, acrylamido-methyl-propane sulfonate derivative polymers,acrylamido-methyl-propane sulfonate co-polymers, and acrylicacid/acrylamido-methyl-propane sulfonate co-polymers and combinationsthereof. Methods of determining suitable aqueous tackifier agents andadditional disclosure on aqueous tackifier agents can be found in U.S.patent application Ser. No. 10/864,061 and filed Jun. 9, 2004 and U.S.patent application Ser. No. 10/864,618 and filed Jun. 9, 2004 therelevant disclosures of which are hereby incorporated by reference.

Silyl-modified polyamide compounds suitable for use as an adhesivesubstance in the methods of the present invention may be described assubstantially self-hardening compositions that are capable of at leastpartially adhering to particulates in the unhardened state, and that arefurther capable of self-hardening themselves to a substantiallynon-tacky state to which individual particulates such as formation fineswill not adhere to, for example, in formation or proppant pack porethroats. Such silyl-modified polyamides may be based, for example, onthe reaction product of a silating compound with a polyamide or amixture of polyamides. The polyamide or mixture of polyamides may be oneor more polyamide intermediate compounds obtained, for example, from thereaction of a polyacid (e.g., diacid or higher) with a polyamine (e.g.,diamine or higher) to form a polyamide polymer with the elimination ofwater. Other suitable silyl-modified polyamides and methods of makingsuch compounds are described in U.S. Pat. No. 6,439,309 issued toMatherly, et al., the relevant disclosure of which is hereinincorporated by reference.

The coated particulates of the present invention may be suspended in anytreatment fluid known in the art, including aqueous gels, viscoelasticsurfactant gels, oleaginous gels, foamed gels and emulsions. Suitableaqueous gels are generally comprised of water and one or more gellingagents. The emulsions may be comprised of two or more immiscible liquidssuch as an aqueous gelled liquid and a liquefied, normally gaseousfluid, such as nitrogen. The preferred treatment fluids for use inaccordance with this invention are aqueous gels comprised of water, agelling agent for gelling the water and increasing its viscosity, andoptionally, a cross-linking agent for cross-linking the gel and furtherincreasing the viscosity of the fluid. The increased viscosity of thegelled or gelled and cross-linked treatment fluid, inter alia, reducesfluid loss and allows the fracturing fluid to transport significantquantities of suspended particulates. The treatment fluids also mayinclude one or more of a variety of well-known additives such asbreakers, stabilizers, fluid loss control additives, clay stabilizers,bactericides, and the like.

Partitioning agents suitable for use in the present invention are thosesubstances that will dissipate once the particulates are introduced to atreatment fluid, such as a fracturing or gravel packing fluid.Partitioning agents suitable for use in the present invention should notdetrimentally interfere with the adhesive substance on the particulate,and should not detrimentally interfere with the treatment fluid or thesubterranean operation being performed. This does not mean that thechosen partitioning agent must be inert. Rather, in some embodiments ofthe present invention the partitioning agent is also a treatmentchemical that has a beneficial effect on the subterranean environment,or the operation, or both. In preferred embodiments, the partitioningagent is coated onto the adhesive substance-coated particulate in anamount of from about 1% to about 20% by weight of the coatedparticulate. In preferred embodiments, the substantially the entiresurface of the adhesive substance coating is coated with partitioningagent.

Partitioning agents suitable for use in the present invention are thosematerials that are capable of coating onto the adhesive substancepre-coating on the particulate and reducing its tacky character.Suitable partitioning agents may be substances that will quicklydissipate in the presence of the treatment fluid. Examples of suitablepartitioning agents that will dissolve quickly in an aqueous treatmentfluid include solid salts (such as rock salt, fine salt, KCl, and othersolid salts known in the art), barium sulfate, lime, benzoic acid,polyvinyl alcohol, sodium carbonate, sodium bicarbonate, molybdenumdisulfide, sodium hydroxide graphite, zinc, lime, quebracho, lignin,lignite, causticized lignite, lignosulfonate, chrome lignosulfonate,napthalenesulfonate, uintahite (gilsonite), polyvinvyl alcohol, andmixtures thereof. One skilled in the art will recognize that where lime(calcium carbonate) is chosen for use as a partitioning agent in thepresent invention it may be used in any of its forms, includingquicklime, hydrated lime, and hydraulic lime. The partitioning agentalso may be a substance that dissipates more slowly in the presence ofthe treatment fluid. Partitioning agents that dissolve more slowly mayallow the operator more time to place the coated particulates. Examplesof suitable partitioning agents that will dissolve more slowly in anaqueous treatment fluid include calcium oxide, degradable polymers, suchas polysaccharides; chitins; chitosans; proteins; aliphatic polyesters;poly(lactides); poly(glycolides); poly(ε-caprolactones);poly(hydroxybutyrates); poly(anhydrides); aliphatic polycarbonates;poly(orthoesters); poly(amino acids); poly(ethylene oxides); andpoly(phosphazenes); and mixtures thereof.

Where the treatment fluid is an oleaginous treatment fluid, examples ofsuitable partitioning agents that will dissolve in an oleaginoustreatment fluid include wax, gilsonite, sulfonated asphalt,naphthalenesulfonate, oil soluble resins, and combinations thereof. Somesuitable oil soluble resins include, but are not limited to,styrene-isoprene copolymers, hydrogenated styrene-isoprene blockcopolymers, styrene ethylene/propylene block copolymers, styreneisobutylene copolymers, styrene-butadiene copolymers, polybutylene,polystyrene, polyethylene-propylene copolymers, and combinationsthereof.

The chosen partitioning agent should be able to at least temporarilyreduce the tacky nature of the adhesive substance coated onto theparticulate, but it may also perform other functions. For example, someembodiments of the present invention coat a particulate with a resin andthen use a partitioning agent that is a resin hardening agent. In otherembodiments the partitioning agent may act as a scale inhibitor,corrosion inhibitor, parrafin remover, gel breaker, crosslink de-linker,gas hydrate inhibitor, or any other solid treatment chemical that can becoated on top of an adhesive substance to at least temporarily reduceits tacky nature.

Moreover, in some embodiments the adhesive substance and partitioningagent may be coated onto a particulate in layers. By way of example, aparticulate may be coated with an adhesive substance and then coatedwith a partitioning agent and then coated again with an adhesivesubstance and then coated again with a partitioning agent. In such acase the first and second coatings of the adhesive substance need not bethe same and the first and second coatings of the partitioning agentneed not be the same. As will be understood by one skilled in the art,more than two layers of adhesive substances and partitioning agents maybe used. This may be particularly useful in situations wherein it isdesirable to delay the release of a partitioning agent that also acts asa treatment chemical. For example, a first (inner) layer of partitioningagent may be a treatment chemical that is a gel breaker and a secondlayer of partitioning agent may be an inert, slowly dissolvingpartitioning agent. Also for example, the first (inner) layer ofpartitioning agent may be a crosslinker, with a second layer ofpartitioning agent being a slowly dissolving partitioning agent. Alsofor example, the first (inner) layer of partitioning agent may be ahardenable resin component, with a second layer being an inertdissolving agent, and a third layer being a hardening agent component.

Some embodiments of the methods of the present invention provide methodsfor treating subterranean formations using partitioned, coatedparticulates wherein the coated particulates are made by substantiallycoating particulates with an adhesive substance to createadhesive-coated particulates and then substantially covering theadhesive-coated particulates with a partitioning agent to createpartitioned, coated particulates.

Suitable partitioned, coated particulates may be used in a variety ofsubterranean treatments including fracturing, gravel packing, andfrac-packing treatments wherein the partitioned, coated particulates aregenerally substantially slurried into a treatment fluid to create apartitioned, coated particulate slurry that may then be placed into adesired location within a portion of a subterranean formation.

To facilitate a better understanding of the present invention, thefollowing examples of some of the preferred embodiments are given. In noway should such examples be read to limit the scope of the invention.

EXAMPLES Example 1

A sample of bauxite particulates was pre-coated with a high temperatureepoxy resin and another sample was pre-coated with a furan resin; eachsample contained 7.8 cc of resin per 250 grams of particulate. Sodiumbicarbonate powder (20 grams) was then covered onto each of the resincoated samples to form coated particulates. The samples of particulateswere stored at room temperature for three days. After that time thesamples, still substantially non-agglomerated, were mixed in anaqueous-based fracturing fluid and formed a slurry concentration of 7pounds of particulates per gallon of fracturing fluid. The sodiumbicarbonate covering dissolved as the particulates were mixed into thefracturing fluid. The coated particulates of the present inventionproved capable of retaining their individual character even after beingstored for a period of time.

The slurry was then crosslinked, stirred for an hour at 180° F., andthen packed into a brass chamber and cured for at least 8 hours at 325°F. Core samples obtained from the cured particulates reflectedconsolidation strength of between 850 and 1,100 psi. Thus, the coveringused to create the coated particulates did not act to impairconsolidation.

Example 2

High-molecular weight polyamide tackifying compound in the amount of 3cc was dry coated directly onto 300 grams of 20/40-mesh Brady sand byhand stirring with a spatula to form a thin film of the compound on thesand grains. Afterward, 20 grams of KCl powder with average particlesize distribution of 40 microns was hand stirred into the coated sanduntil the coated sand became dry. A sample of this dry coated sand wasthen mixed with water. The tackiness immediately returned to the coatedsand.

Example 3

Low-molecular weight polyamide tackifying compound in the amount of 3 ccwas dry coated directly onto 300 grams of 20/40-mesh Brady sand by handstirring with a spatula to form a thin film of the compound on the sandgrains. Afterward, 20 grams of KCl powder with average particle sizedistribution of 40 microns was hand stirred into the coated sand untilthe coated sand became dry. A sample of this dry coated sand was thenmixed with water. The coated sand immediately became tacky again.

Therefore, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosethat are inherent therein. While numerous changes may be made by thoseskilled in the art, such changes are encompassed within the spirit andscope of this invention as defined by the appended claims.

1. A method of treating a portion of a subterranean formationcomprising: providing partitioned, coated particulates that compriseparticulates, an adhesive substance, and a partitioning agent, andwherein the partitioning agent comprises a subterranean treatmentchemical; substantially slurrying the partitioned, coated particulatesin a treatment fluid to create a particulate slurry; and, placing theparticulate slurry into the portion of the subterranean formation. 2.The method of claim 1 wherein the method by which the partitioned,coated particulates are made comprises: substantially coating theparticulates with an adhesive substance to create adhesive-coatedparticulates and then substantially covering the adhesive-coatedparticulates with a partitioning agent to create partitioned, coatedparticulates.
 3. The method of claim 2 wherein the partitioned, coatedparticulates comprise more than one alternating layers of adhesivesubstance and partitioning agent.
 4. The method of claim 1 wherein theparticulates comprise at least one of the following: low qualityparticulates; sand; bauxite; ceramic materials; glass materials; polymermaterials; Teflon® materials; nut shell pieces; seed shell pieces; curedresinous particulates comprising nut shell pieces; cured resinousparticulates comprising seed shell pieces; fruit pit pieces; curedresinous particulates comprising fruit pit pieces; wood; or compositeparticulates.
 5. The method of claim 1 wherein the adhesive substance isa resin and wherein the resin comprises a two-component epoxy-basedresin, a furan-based resin, a phenolic-based resin, a high-temperature(HT) epoxy-based resin, a phenol/phenol formaldehyde/furfuryl alcoholresin, or a combination thereof.
 6. The method of claim 1 wherein theadhesive substance comprises ate least one of the following: an aqueoustackifying agent, a non-aqueous tackifying agent, or a silyl-modifiedpolyamide.
 7. The method of claim 6 wherein the aqueous tackifying agentcomprises at least one of: an acrylic acid polymer, an acrylic acidester polymer, an acrylic acid derivative polymer, an acrylic acidhomopolymer, an acrylic acid ester homopolymer, an acrylic acid estercopolymer, a methacrylic acid derivative polymer, a methacrylic acidhomopolymer, a methacrylic acid ester homopolymer, anacrylamido-methyl-propane sulfonate polymer, anacrylamido-methyl-propane sulfonate derivative polymer, anacrylamido-methyl-propane sulfonate copolymer, or an acrylicacid/acrylamido-methyl-propane sulfonate copolymer.
 8. The method ofclaim 6 wherein the non-aqueous tackifier agent comprises at least oneof: a polyamide, a polyester, a polycarbonate, polycarbamate, or anatural resin.
 9. The method of claim 6 wherein the aqueous tackifyingagent comprises at least one of: a poly(methyl acrylate), a poly(butylacrylate), a poly(2-ethylhexyl acrylate); a poly(methyl methacrylate), apoly(butyl methacrylate), or a poly(2-ethylhexyl methacryate).
 10. Themethod of claim 6 wherein the silyl-modified polyamide comprises areaction product of a silating compound with a polyamide or a mixture ofpolyamides.
 11. The method of claim 1 wherein the subterranean treatmentchemical comprises at least one of the following: a scale inhibitor, abreaker, a corrosion inhibitor, a paraffin remover, a gel breaker, acrosslink de-linker, or a gas hydrate inhibitor.
 12. The method of claim1 wherein the treatment fluid comprises an aqueous gel, a viscoelasticsurfactant gel, an oleaginous gel, a foamed gel, or an emulsion.
 13. Amethod of creating a propped fracture in a portion of a subterraneanformation comprising: providing at least one fracture in the portion ofthe subterranean formation; providing partitioned, coated particulatesthat comprise particulates, an adhesive substance, and a partitioningagent, and wherein the partitioning agent comprises a subterraneantreatment chemical; substantially slurrying the partitioned, coatedparticulates in a treatment fluid to create a particulate slurry; and,placing the particulate slurry into the at least one fracture in theportion of the subterranean formation so as to deposit at least aportion of the partitioned, coated particulates into the at least onefracture.
 14. The method of claim 13 wherein the method by which thepartitioned, coated particulates are made comprises: substantiallycoating the particulates with an adhesive substance to createadhesive-coated particulates and then substantially covering theadhesive-coated particulates with a partitioning agent to createpartitioned, coated particulates.
 15. The method of claim 14 wherein thepartitioned, coated particulates comprise more than one alternatinglayers of adhesive substance and partitioning agent.
 16. The method ofclaim 13 wherein the treatment chemical comprises at least one of thefollowing: a scale inhibitor, a breaker, a corrosion inhibitor, aparaffin remover, a gel breaker, a crosslink de-linker, or a gas hydrateinhibitor.
 17. The method of claim 13 wherein the partitioning agentcomprises at least one of the following: calcium oxide, a degradablepolymer, a poly(glycolide); a poly(ε-caprolactone); apoly(hydroxybutyrate); a poly(anhydride); an aliphatic polycarbonate; apoly(orthoester); a poly(amino acid); a poly(ethylene oxide); apoly(phosphazene); a solid salt; barium sulfate; lime; benzoic acid;polyvinyl alcohol; sodium carbonate; sodium bicarbonate; molybdenumdisulfide; sodium hydroxide graphite; zinc; quebracho; lignin; lignite;causticized lignite; lignosulfonate; chrome lignosulfonate;napthalenesulfonate; uintahite; polyvinvyl alcohol; wax; gilsonite;sulfonated asphalt; an oil-soluble resin; a styrene-isoprene copolymer;a hydrogenated styrene-isoprene block copolymer; a styreneethylene/propylene block copolymer; a styrene isobutylene copolymer; astyrene-butadiene copolymer; polybutylene; polystyrene; or apolyethylene-propylene copolymer.
 18. A method of gravel packing along aportion of a well bore comprising: providing a portion of a well bore;providing partitioned, coated particulates that comprise particulates,an adhesive substance, and a partitioning agent, and wherein thepartitioning agent comprises a subterranean treatment chemical;substantially slurrying the partitioned, coated particulates in atreatment fluid to create a particulate slurry; and, placing theparticulate slurry into the portion of the well bore so as to deposit atleast a portion of the partitioned, coated particulates into thatportion and to create a gravel pack therein.
 19. The method of claim 18wherein the method by which the partitioned, coated particulates aremade comprises: substantially coating the particulates with an adhesivesubstance to create adhesive-coated particulates and then substantiallycovering the adhesive-coated particulates with a partitioning agent tocreate partitioned, coated particulates.
 20. The method of claim 19wherein the partitioned, coated particulates comprise more than onealternating layers of adhesive substance and partitioning agent.
 21. Themethod of claim 18 wherein the treatment chemical comprises at least oneof the following: a scale inhibitor, a breaker, a corrosion inhibitor, aparaffin remover, a gel breaker, a crosslink de-linker, or a gas hydrateinhibitor.
 22. The method of claim 18 wherein the partitioning agentcomprises at least one of the following: calcium oxide, a degradablepolymer, a poly(glycolide); a poly(β-caprolactone); apoly(hydroxybutyrate); a poly(anhydride); an aliphatic polycarbonate; apoly(orthoester); a poly(amino acid); a poly(ethylene oxide); apoly(phosphazene); a solid salt; barium sulfate; lime; benzoic acid;polyvinyl alcohol; sodium carbonate; sodium bicarbonate; molybdenumdisulfide; sodium hydroxide graphite; zinc; quebracho; lignin; lignite;causticized lignite; lignosulfonate; chrome lignosulfonate;napthalenesulfonate; uintahite; polyvinvyl alcohol; wax; gilsonite;sulfonated asphalt; an oil-soluble resin; a styrene-isoprene copolymer;a hydrogenated styrene-isoprene block copolymer; a styreneethylene/propylene block copolymer; a styrene isobutylene copolymer; astyrene-butadiene copolymer; polybutylene; polystyrene; or apolyethylene-propylene copolymer